Rotary actuator, especially for adjustable furniture, including beds and bottom for beds

ABSTRACT

A rotary actuator, in particular for adjustable articles of furniture, including beds or mattress supports, for incorporation in a structure for adjustment of an element in it, e.g. adjustment of a backrest section and/or leg-rest section in a bed or mattress support, said actuator comprising an electric motor ( 20 ) which is connected by a drive shaft with a transmission ( 21 ), which is in turn connected by a power take-off with a planetary gear having a sun wheel ( 54 ) connected with the power take-off of the transmission, first and second internally toothed outer rings ( 49 ) which are rigidly interconnected and have the same toothing, an internally toothed intermediate ring ( 50 ) positioned between the first and second outer rings so that it can rotate about its axis relative to the outer rings, a plurality of planet wheels ( 51 ) in engagement with the two outer rings and the intermediate ring and the sun wheel, and wherein the intermediate ring has a mounting bracket ( 11 ) for connection with one part of the structure, and wherein the outer rings or their rigid connection has a mounting bracket ( 12 ) for connection with the other part of the structure. A strong and comparatively noiseless as well as relatively inexpensive rotary actuator may be provided hereby. It may be constructed with a jamming protection arrangement and emergency lowering function.

The present invention relates to a rotary actuator, in particular foradjustable articles of furniture, including beds or mattress supports,for incorporation in a structure for adjustment of an element in it,e.g. adjustment of a backrest section and/or legrest section in a bed ormattress support.

On beds, no matter whether they are hospital beds or care beds ormattress supports for domestic use having an adjustable head end andtypically also an adjustable foot end, it is common that the adjustmentis carried out by means of linear actuators. An example of a hospitalbed is found in EP 498 111 to J. Nesbit Evans (the name has been changedto Huntleigh Technology Plc), and an example of an actuator is found inEP 577 541 to Linak A/S. A special embodiment for separate mattresssupports is seen in DE 38 42 078 to Niko (the name has been changed toOKIN). The actuators require much space, which is a drawbackparticularly in beds and mattress supports for domestic use. It appliesto hospital beds that these have to be washed from time to time, whichtakes place at a temperature of 65° C. in washing machines intended forthe purpose. This makes special demands on the electrical adjustmentmechanisms and the associated control equipment. These must inter aliabe water-tight.

WO 99/40820 to Recticel discloses another example of an adjustmentmechanism in which a tube shaft is rotated by means of a motor arrangedat the end thereof. The structure has not been realized because ofproblems with the drive unit.

WO 92/20548 to Linvent AB discloses a drive of the above-mentioned type.This drive, which is based on a planetary gear structure, isparticularly intended for front seats in cars, said drive serving as amounting bracket for the backrest at one side and to adjust theinclination of the backrest.

In summary, the requirements to be met by adjustment mechanisms for bedsare that they must have a relatively great strength, and that at thesame time hey must be compact and comparatively noiseless as well aseasy to mount. In addition, they must be capable of being constructed asa low volt structure. Further, the price must below.

The object of the invention is to provide a rotary actuator of the typementioned in the opening paragraph which is capable of satisfying thesedifferent requirements. Also, it must be possible to manufacture theactuator at production costs which at least do not give a considerablyhigher price than the operationally reliable and well-tested linearactuators.

This is achieved according to the invention by a rotary actuator asdefined in claim 1. It is hereby possible to use the same motor type asin linear actuators, i.e. a low volt motor having a relatively highnumber of revolutions which is reduced in the subsequent transmission.The planetary gear itself can be made relatively small and yet be ableto transfer great forces, as the two outer rings distribute the forcesmore evenly in the gear and also support the planet wheels and theintermediate ring.

By providing the planetary gear with the number of teeth stated inclaims 2-7 a high transmission reduction is achieved, and also a goodtransfer of forces may be achieved by shaping the planet wheels suchthat over their entire length they engage the toothed rims. It alsosimplifies the manufacture when the planet wheels have the samecross-section over the entire length. With the concretely stated numberof teeth, a transmission of 1:53.2 is achieved. The central arrangementof the sun wheel has a stabilizing effect and also contributes to a gooddistribution of forces.

The two outer rings may be connected in various ways, e.g. with acombination of bolts and spacers, fishplates or integration in a tubemember. Expediently, however, they are provided in or as a commonhousing which may readily be designed such that the mounting bracket maybe secured on the end thereof. This gives an evident possibility ofconstructing the actuator such that it may be mounted at the end of atube.

The actuator will readily be able to transfer the occurring forces ifthe planetary gear is made of machine steel and is tempered, but themanufacturing costs will be so high that the price per se will be anobstacle to the use of the actuator in furniture structures.

When, according to the invention, the planetary gear is made of sinteredmetal, a more reasonable production price may be achieved. The two outerrings may be made as two parts, each having a width, calculated in thelongitudinal direction of the toothed rims, which is attractive forsintered metal manufacture, there being an upper limit to the height ofthe parts during pressing.

The two outer rings may be made as two halves which are assembled to aunit. Alternatively, two identical outer parts with an intermediatespacer, which also provides the opening for the mounting bracket of theintermediate ring. When the faces of the parts directed toward eachother are formed with a pattern of male/female parts, these are securedagainst mutual rotation when they are clamped together. The splittingalso makes it easier to manufacture the parts of sintered metal.

When, according to the invention, the parts with the two outer rings aremade of plastics and the toothed rims themselves as an insert ofsintered metal, a further reduction in the manufacturing costs may beachieved. It is hereby possible to make a single part of plastics withrecesses for the toothed rims. To retain the toothed rims in theplastics part, the connection is provided as a splined connection sothat the toothed rims may be inserted from the ends.

When, according to the invention, the ends of the toothed rims facingeach other and the intermediate ring are formed with cooperating steppedarrangements, a good mutual control of these is achieved. The steppedarrangements are expediently made as a single step in that the toothedrims have an internal step at one end and an external step at theopposite end. The part will hereby have the same height throughout,which is advantageous for sintering.

In an embodiment, the planet wheels are made of sintered metal andcarried by a steel shaft. In that case, however, it has been foundadvantageous to provide the planet wheels with a bearing bushing. Theplanet wheels are relatively long and border on what is possible withsintered metal. A better accuracy is achieved by making the planetwheels as two halves and assembling these on the shaft.

In an embodiment of the actuator according to the invention, themounting brackets of the two outer rings and the intermediate ring areformed as arms for connection with the movable part and the stationarypart, respectively, of the structure in which they are to beincorporated. Expediently, the arm of the outer rings is formed by platematerial, mounted on a free end of one of the two outer rings. The armof the intermediate ring is likewise expediently formed by a plate, theactual toothed rim being formed as an insert inserted into a recess inthe plate material. In terms of costs, this is less expensive thanmaking the intermediate ring and the arm as an integrated unit ofsintered metal. A special structure consists of two relatively thinplates with flared edges and hole rim and assembled with the plane sidesagainst each other. The flared hole rim simultaneously serves as a goodguide for the insert of sintered metal. In the pressing, the flared holerim may be formed with a spline for the fixing of the insert, which isformed with a corresponding spline. If the conditions of load permit;the arm may also be made of plastics, optionally with a single embeddedmetal plate as a support. For reasons of strength, however, it has beenfound expedient to make the arm of a stack of punched metal plates,preferably three. Another option is to make the arm of a thick laser-cutplate.

It will be appreciated that the actuator may be constructed such thatthe outer rings are fixed in the structure in which the actuator is tobe incorporated, while the intermediate ring drives the movable elementin the structure. The actuator may also be constructed conversely, sothat the intermediate ring is fixed, while the outer rings drive themovable element.

According to the invention, the actuator is driven by an electric motor.This is typically a low volt motor according to the power currentregulation, i.e. below 42.4 volts. A step-down transmission is typicallyinterposed between the motor and the furniture drive, as the motorusually has a high number of revolutions. The motor and the transmissionare expediently secured to a free end of one of the two outer rings,preferably so that the motor, the transmission and the outer rings arearranged on a common axis. This structure makes the actuator suitablefor mounting at the end of a tube, e.g. so that the outer rings and theintermediate ring are disposed externally of the tube end, while thetransmission and the motor are disposed inside the tube. However, theactuator may also be constructed such that also the outer rings and theintermediate ring are disposed completely inside the tube. The mountingbracket of the intermediate ring is then constructed as a carrier inengagement with the tube. This, internal arrangement provides a goodpossibility of achieving a moisture- or water-tight structure.

When, according to the invention, the motor is provided with radiallyprotruding legs of an elastic material, preferably in the form of a beltwith protruding legs which are pushed inwardly over the motor, said leasbeing intended for cooperation with the inner side of the tube intowhich the motor is inserted, a simple and vibration-damping support ofthe motor is achieved.

The subclaims define additional expedient structures of the actuator,and the advantages of these will appear from the description of theembodiment of the invention.

The invention will be explained more fully below with reference to theembodiment illustrated in the accompanying drawing. In the drawing:

FIG. 1 shows a mattress support intended to be placed or incorporated ina bed,

FIG. 2 shows a rotary actuator in its entirety,

FIG. 3 shows a longitudinal section through the drive unit of theactuator,

FIG. 4 shows a lateral view of the motor with the two first links in thetransmission,

FIG. 5 shows a cross-section of FIG. 4 through worm/bevel wheels seeninwards toward crone wheel,

FIG. 6 shows a longitudinal section through the end of the tube withpower supply and control electronics,

FIG. 7 shows a longitudinal section through another embodiment of therotary actuator according to the zone invention,

FIG. 8 shows a section along the line VIII—VIII in FIG. 7,

FIG. 9 shows a perspective view of the actuator in FIG. 7 from the motorend,

FIG. 10 shows a longitudinal section through end stop switches,

FIG. 11 shows a longitudinal section through another embodiment of theend stop switches,

FIG. 12 shows a perspective view of a bed with another embodiment of therotary actuator according to the invention,

FIG. 13 shows a longitudinal section through the outer part of the driveof the actuator,

FIG. 14 shows a cross-section along the line XIV—XIV in FIG. 13,

FIG. 15 shows an exploded view of parts of the outer planetary gear,

FIG. 16a shows a perspective view of a part for the drive,

FIG. 16b shows the same as FIG. 16a, but seen from the other end, and

FIG. 17 shows an exploded view of parts for the drive.

The mattress support shown in FIG. 1 comprises an outer frame 1 whichincludes a mattress support portion consisting of a pivotable backrestpart 2, a fixed central part 3 and a legrest part 4 which isarticulated. The central part 3 is fixedly mounted on the sides of theouter frame 1.

The backrest part 2 is pivotable about a shaft 5 secured at the sides ofthe outer frame 1, and correspondingly the legrest part is pivotableabout a shaft 6. Both the backrest part 2 and the legrest part 3 may beadjusted by a rotary actuator 7, as shown in FIG. 2. The rotary actuatorcomprises an extruded aluminium tube 10 of square cross-section, atwhose one end there is a drive unit with a driven arm 11. An arm 12 issecured at each end of the tube 10, and, at the end with the drive unit,the arm is secured to the outer side thereof. At the backrest part 2,the arm is equipped with a wheel 13 which is guided in a guide rail 14secured to the backrest part. The tube 10 is rotatably mounted about itslongitudinal axis in a bracket 15 secured at each side of the outerframe 1. As the other arm 11 of the actuator is fixed, the tube 10 andthe arms 12 secured on the end thereof will rotate when the actuator isactivated. The arms 12 will hereby raise or lower the backrest part, asthis will pivot about its shaft 5. The legrest part is raised or loweredin a corresponding manner, as the ends of the arms 12 a on the actuator7 b of the legrest part are rotatably secured to a bracket on theoutermost link 4 a of the legrest part. Activation of the actuator willcause the legrest part 4 to be raised or lowered, as the arm 12 b willcause the innermost link 4 b to rotate about the shaft 6 through araising and rotating movement of the outermost link 4 a of the legrestpart.

As will appear from FIG. 3, the drive unit consists of an electric motor20, a transmission 21 consisting of three links 22, 23, 24 and finally aspecially constructed planetary gear 25 with the arms 11, 12. The twofirst transmission stages 22, 23 are integrated in the front cover ofthe motor. The first stage is a worm gear where the worm 26 is providedin an extension of the motor shaft. The end of the worm is guided in asliding bearing 27 in a bracket 28. The worm drives two pairs of wormwheels 29 arranged on their respective sides of it. The worm wheels aremoulded integrally with a bevel wheel 30. Worm/bevel wheels 29, 30 aremounted on a shaft 31 which is arranged in a bracket 32 on the frontcover. The worm wheels drive a crown wheel 33 mounted on the end of thebracket 28, which is formed as a journal 34. The crown wheel is mouldedintegrally with a sun wheel 35, and the unit is secured on the journalby a locking washer. All the gear wheels are moulded of plasticsmaterial, while the worm is of steel.

The two first transmission steps 22, 23 are contained in a first chamber36 in a housing 37 with an intermediate wall 38 to a second chamber 39.The outer end of the crown wheel extends through a bore 41 in theintermediate wall 38: The housing as a whole is secured on the frontcover 42 of the motor by snap lock connections in the form of snaplocking legs 43 on the cover which engage mating recesses 44 in the sidewall of the housing.

The third stage 24 in the transmission is formed by an ordinaryplanetary gear, where the sun wheel is formed by the sun wheel 35 on thecrown wheel of the preceding link. The sun wheel engages a planet wheel45, which is in turn in engagement with an internal toothing 46 in thehousing.

The next member is the outer planetary gear 25 consisting of a plasticshousing 47 with an opening for the arm 11. The housing accommodates twoouter rings 49 secured against rotation in the housing through a splinedconnection. A free rotatable intermediate ring 50 is arranged betweenthe two outer rings 49. The rinds are made of sintered metal, and on theedges facing each other they have a stepped arrangement 79 forcontrolling the intermediate ring. The arm 11 is made of three joinedsteel plates in which a hole has been punched for the intermediate ring50. The intermediate ring and the arm are likewise connected in anon-rotatable manner through a splined connection. The outer rings 49have an internal toothing with 41 teeth and the intermediate ring 50 aninternal toothing with 45 teeth. Four planet wheels are engaged with therings 49, 50 and have the same toothing over the entire length, viz. 16teeth. The planet wheels are made of sintered metal and with a bushingof plastics mounted on a steel shaft and assembled on steel ring at eachend. The planet wheels 51 are engaged with a sun wheel 54 likewise ofsintered metal and positioned centrally in the planetary gear to achieveas even a distribution of the forces therein as possible. The sun wheelis welded on a short steel shaft 55, and a solid cylinder member 56,likewise of sintered metal and having a toothing, is welded on the otherend thereof. The planetary gear is connected with the precedingtransmission 24 in that the cylinder member 56 is receiver n anon-rotatable manner in a well 57 integrated with the planet wheels inthe transmission 24. The sun wheel 54 is kept in position by the bottomof a well 65 on an intermediate cover 66, which also retains theexternal outer ring 49 a. The entire plastics housing 47 is terminatedby an end cover 67 provided at the end of the arm 12 a. The cover part67 of the arm accommodates a bearing bushing 88 for attachment to thebracket 15 on the bed frame.

The outer planetary gear 25 is secured on the other part of the drive bya collar 59 on the housing 37. This collar also keeps the internal outerring 49 b in position. The collar is secured by a snap lock 60 in theplastics housing 47 of the planetary gear.

It will thus be appreciated that the entire drive with motor,transmission and outer planetary gear constitutes a unit which issecured by screws 61 on the end of the aluminium tube 10, the screwsbeing screwed into screw channels 62 at the internal corners of thealuminium tube. In the present case, an intermediate member 63 isinterposed between the aluminium tube 10 and the plastics housing 47. Aswill appear, for fixing purposes, the plastics housing 47 has a neck 64which fits the end of the intermediate member 63.

With reference to FIG. 6, a cabinet 70 is inserted at the other end ofthe tube 10, said cabinet having a cross-section which matches theinternal cross-section of the tube. The cabinet consists of a lower part71 with a cover and is divided into two compartments 72, 73, onecontaining the transformer 74, the other containing the controlelectronics 75. The end of the cabinet has a protruding edge 76 forengagement with the end of the tube. The whole is secured by the arm 12b, whose end is formed as a cover 77 secured by screws which are seatedin the screw channels of the tube. The cover part 77 of the armaccommodates a shaft bushing 78 for attachment of the tube in the bedframe.

FIG. 7 of the drawing shows a slightly different embodiment of therotary actuator according to the invention, and the same referencenumerals as in the foregoing are used for the same parts. The embodimentessentially differs in that the transmission between the motor 20 andthe outer planetary gear 25 is formed by a gear train consisting ofthree planetary gears 80, 81, 82, the motor shaft being provided with asun wheel 83 in the first planetary gear. Otherwise, the planetary gearsconventionally have sun wheels, planet wheels and an internally toothedrim. The toothed rims are here provided in the common housing. Also likebefore, the sun wheel in the outer planetary gear is coupled to theplanet wheels in the last planetary gear 82.

The sun wheel 83 on the motor shaft, which is made of a relatively softplastics material for reasons of noise, is moulded on a metal bushingwith a knurling, carriers or the like for non-rotational mounting. Thisresults in a better attachment on the motor shaft and also causes theheat to be conducted more effectively away from the plastics wheel,otherwise the soft plastics required for noise reduction could not beused.

For noise reduction, the gear train is of plastics. To achieve thedesired gearing and to achieve a noise reduction as great as possible,it has been found expedient with the following gearings in the geartrains, where the first link has a gearing of about 1:6.8, the secondlink a gearing of about 1:5.8, and the third link a gearing of about1:3.7, i.e. a total gearing of about 1:145.

To reduce the noise from the motor and to avoid the situation that thisstrikes against the inner side of the tube 10, the free end of the motor20 inside the tube is fixed by a support 90 of rubber, cf. FIG. 9. Thesupport consists of a ring 91 which is pushed inwardly over the end ofthe motor housing. The ring has four blocks 92 which, with a concavesurface, are engaged with and are fixed against the screw channels inthe corners of the tube. Rearwardly, the support has a ring 93 whichengages the rear side of the motor. The two rings 90, 93 are kepttogether by four straps 94.

Reference is now made to FIGS. 9 and 10. For controlling the endpositions of the actuator, the side of the housing 37 with thetransmission has secured thereon a housing 100 having two end stopswitches 101, 102 operated by a longitudinally slidable pin 103, whichis spring-loaded by a coil spring 104 to a neutral position. The pin hasa hole 105 which accommodates a rocker arm 106 in which a leaf spring107 is mounted, said leaf spring engaging a push-button on the end stopswitches 101, 102. The inner-most end 108 of the pin engages a cam faceon the edge of a cam 109. This cam is secured to the side of the arm 11.It is indicated in FIG. 3 that on each side of the part of the arm 11that accommodates the intermediate ring 50, two bearing rings areinserted into the housing 47, one of which bearing rings may be shapedas the cam, or it may be a separate element. At one end position the pinis moved to the right by the cam, causing the arm to press the leafspring down on the switch 102 to the right and to activate it. At theother end position, the spring moves the pin to she left, causing theleft-hand switch 101 to be activated. Therebetween, the pin is in aneutral position. The switches activate the control circuit to interruptthe current to the motor. The fraction of lag in the actuatorcontributes to ensuring that the cam does not run back so that the pindoes not prematurely release its contact with the face concerned on thecam. A slightly different embodiment is shown in FIG. 11, where thespring 104 is mounted in a recess in the housing 47, and the leaf springis replaced by a double rocker arm 110.

If the actuator does not posses the necessary self-blocking capacity forthe arm to maintain the position concerned when the motor is switchedoff, then the actuator may be provided with a brake spring 120 in theform of a coil spring which, with a plurality of windings, here four, iswound around a cylindrical element 121 secured to the well 57 whichconnects the transmission with the outer planetary gear 25. One end ofthe spring is fixed in the housing. The braking force of the spring isadjusted so that it presents no or almost no resistance when theactuator is activated to raise the backrest part 2 or the legrest part 4of the mattress support portion. When the current to the motor isinterrupted, the spring will exert a sufficient braking force to keepthe backrest part 2 or legrest part 4 in the given position. Forlowering, the motor must merely use relatively modest energy to overcomethe braking force.

Reference is now made to FIGS. 1, 2 and in particular 9. The actuatorsfor the backrest part 2 and the legrest part 4 are positioned in themattress support so that the arm 11 is on a straight line, which ispossible in that the arms 11, 12 are symmetrical about theirlongitudinal axes. The arm is rotatable connected with a U-profile 130by a bolt 131, said arm resting with one edge on the bottom of theU-profile. The other end of the U-profile 130 is slidably mounted in atube 132 of quadrangular cross-section. This tube 132 connects the arms11 of the two actuators with each other. When e.g. the backrest partactuator is activated, the torque will be accommodated in thisconnecting tube 132. If anything gets jammed between e.g. the backrestpart 2 and the bed frame 1, the backrest part will stand still and thearm 11 will instead begin to rotate relative to the U-profile 130 andpull it outwards in the tube 132. The U-profile may be mounted looselyin the tube, or there may be a through bolt which is positioned througha slot either in the side wall of the tube or in the U-profile, so thatthe profiles cannot be pulled apart by accident. When the backrest partstands still, the user will quickly realize that something has gotjammed and will be able to stop the actuator. To remove the object whichis stuck, it may be expedient to move the backrest part slightlyupwards. The same applies to the legrest part.

It is noted that the drawings of the actuator are substantially in theorder of 1:1.

FIGS. 12-17 of the drawing show another embodiment of the actuatoraccording to the invention where the drive unit is arranged entirelywithin the tube. The motor and the transmission are not shown in thefigure, which just shows the outermost part with the outer planetarygear 25. The same reference numerals are used for the same components.Here too, the two outer rings 49 are mounted in a housing 47, which ishere a cylindrical steel housing, and correspondingly to the previousexample the intermediate ring 50 is mounted between the two outer rings.The mounting bracket of the intermediate ring 50 is here shaped as acarrier 140 in the form of a fin in engagement with the inner side ofthe tube in engagement between two screw channels 62 a, 62 b. Theplanetary gear is centered in the tube with two bearing rings 141 a, 141b. One bearing ring 141 b is provided with snap locking legs forcoupling the two rings together. The end of the tube is likewise closedby a cover part 67 of the arm 12. The cover part here has an internaltube part 142 which is positioned over another tube part 143 on a cap144. The two tube parts are mutually secured by snap locking means 145and are additionally mutually non-rotatably fixed via a toothedconnection 146. The cap 144 is provided with snap locking legs and issecured at the end of the ring 141 b. For the sake of illustration,however, the cap is shown in FIGS. 16a, 16 b in a slightly otherembodiment than the one shown in FIG. 13.

The actuator is also provided with an emergency lowering device or quickrelease device based on a coupling spring 148 mounted on a cylindricalpart 147 of the cap. The coupling spring 148 is mounted at its ends inincisions 149 in a cylindrical wall 163 on the intermediate cover 56, inwhich a connecting element 56 is additionally arranged. This ringengages the ring on the end cover 163 by a toothing. For the sake ofgood order it is noted that the structure of this in FIG. 17 is slightlydifferent from the one shown in FIG. 13. The cylindrical tube part 143accommodates a tube shaft 15 connected with a bracket 152 for mountingon the bed frame with screws. A stem 154 extends through a central hole153 in the bracket and is screwed into a hole in the intermediate cover56 with its innermost end, while the other end of the stem 154 extendsbeyond the side of the bed frame and is provided with a pull ring 157. Acoil spring 158, which keeps the intermediate cover 56 in position, isprovided around the stem 154. In ordinary operation, the outer rings 49stand still, while the intermediate ring 50 moves and, via the carrier140, rotates the tube and thereby the arm 12 to raise and lower thebackrest part 2 or the legrest part 4 of the mattress support.

Furthermore, a jamming protection arrangement is provided in theactuator in that the edge of the housing 47 and the rim of theintermediate cover 156 have cooperating carrier teeth 160. When thebackrest part 2 or the legrest part 4 is raised, the teeth with axial orapproximately axial faces are in mutual engagement. When the backrestpart 2 or the legrest part is lowered, the teeth tread on each otherwith an inclined face. If anything gets jammed, the teeth will ride oneach other, and the intermediate cover 56 will be urged away against thespring force which keeps the two sets of teeth in engagement. By thesound of the two sets of teeth riding on each other, and because of thecircumstance that the backrest part or the legrest part stands still,the user will realize that something has got jammed. Like before, thepart is moved slightly upwards to facilitate removal of the jammedobject.

The emergency lowering arrangement operates as follows: In case of anemergency situation where the backrest part 2 or the legrest part 4 isto be lowered, the stem 154 is pulled out, thereby causing the couplingspring 148 to be tightened. Normally, the ends of the spring are seatedin the wide part of the incisions 149 in which a cam face 159 isprovided such that the more the stem is pulled, the greater the couplingforce is. This results in a controlled lowering of the backrest part 2or the legrest part 4. For better understanding of the quick releasefunction and the jamming protection, some parts of the structure areshown in FIG. 17. It is noted that these correspond to FIG. 14 in termsof function, but the cylindrical part on the intermediate cover 56 ishere shaped as a ring 161 which accommodates an insert 150, againconnected non-rotatably with a toothed connection. The tube shaft 151 ishere screwed into the insert 150 with the threads 164. The couplingspring. 148 is loose on the cylindrical part 147 of the cap in normaloperation, i.e. there is no rotational connection with the outer ring 49via the ring 161 of the intermediate cover. When the stem 154 is pulled,the intermediate cover 50 is disengaged from the housing 47, and thecoupling spring 148 is tightened to firmly grip the cylindrical part 147on the cap 144. Via the frame, the arm 12 will now be free to rotatedown to the starting position. It is intended that it must take acertain weight to rotate the arm downwards. The size of the weight maybe determined by the diameter of the spring, which is obtainable injumps of ranges down to {fraction (1/10)} mm.

As will readily be appreciated, this embodiment of the rotary actuatoris extremely easy to make watertight. This can be done solely with theO-rings 170, 171 and the gasket 172: This embodiment of the actuator,which is watertight (IP66), and which has jamming protection andcontrolled emergency lowering, is thus suitable for hospital beds.

It will be appreciated that the invention may be realized in otherconnections than beds or mattress supports, and it will also beappreciated that the invention may be implemented in variousembodiments. The rotary actuator is expediently constructed as anindependent component intended for direct incorporation in a furniturestructure, which should here be understood in the broadest possiblesense. Be it articles of furniture for private dwellings, institutions,hospitals, health centres, dental clinics, seats for vehicles, etc. Theuse of the actuator, however, is not limited to this, as it may also beused in machines, implements, process equipment, and in buildings, e.g.to open windows, doors.

The actuator is here illustrated with a tube shaft and with in-linemotor and transmission, but it will be appreciated that the embodimentmay be adapted as desired. For example, the motor may be arrangedaxis-parallel with the planetary gear, and the transmission may bearranged in the vertical plane at the end of these. The whole may thenbe encapsulated in an almost quadrangular housing. It is also evidentthat the actuator may be provided as indicated in FIG. 3 in a short tubemember in which an end cover is mounted at the end thereof.

What is claimed is:
 1. A rotary actuator, in particular for adjustablearticles of furniture, including beds or mattress supports, forincorporation in a structure for adjustment of an element in it, e.g.adjustment of a backrest section (2) and/or legrest section (4) in a bedor mattress support, said actuator comprising an electric motor (20)which is connected by a drive shaft to a transmission which is in turnconnected by a power take-off to a planetary gear (25) with a sun wheel(54) connected with the power take-off of the transmission, first andsecond internally toothed outer rings (49) which are rigidlyinterconnected (47) and have the same toothing, an internally toothedintermediate ring (50) positioned between the first and second outerrings so that it can rotate about its axis relative to the outer rings,a plurality of planet wheels (51) in engagement with the two outer rings(49) and the intermediate ring (50) as well as the sun wheel (54), andwherein the intermediate ring (50) has a mounting bracket (11) forconnection with one part of the structure, and wherein the outer rings(49) or their rigid connection has a mounting bracket (12) forconnection with the other part of the structure.
 2. An actuatoraccording to claim 1, characterized in that the planet wheels (51) havethe same toothing at the two outer rings and at the intermediate ring,and that the outer rings (49) have a smaller number of teeth than theintermediate ring (50).
 3. An actuator according to claim 2,characterized in that the planet wheels (51) have the same cross-sectionover their entire length.
 4. An actuator according to claim 2,characterized in that the outer rings (49) have a number of teethsmaller than the intermediate ring (50) corresponding to the number ofplanet wheels (51).
 5. An actuator according to claim 3, characterizedin that the outer rings have 41 teeth and the intermediate ring 45teeth, and that four planet wheels are provided.
 6. An actuatoraccording to claim 5, characterized in that the planet wheels have 16teeth and the sun wheel 11 teeth.
 7. An actuator according to claim 1,characterized in that the sun wheel (54), seen in the longitudinaldirection of the actuator, is arranged in the centre of the planetarygear.
 8. An actuator according to claim 1, characterized in that the twoouter rings (49) are provided in or as a common housing (47).
 9. Anactuator according to claim 1, characterized in that the two outer ringsare made as two parts, and wherein the faces of the parts directedtoward each other are formed with a pattern of male/female partsengaging each other.
 10. An actuator according to claim 8, characterizedin that the two outer rings are made of plastics, preferably as a singlepart, and that the toothed rims of the two outer rings are formed asinserts of sintered metal, preferably secured by a splined connection.11. An actuator according to claim 1, characterized in that the ends ofthe toothed rims facing each other are formed with cooperating steppedarrangements (79), expediently as a single step, in that the toothedrims have an internal step at one end and an external step at the otherend.
 12. An actuator according to claim 1, characterized in that the twoouter rings (49, 50) and the intermediate ring are provided with theirrespective arms (11, 12) for connection with the movable part and thestationary part, respectively, of the structure in which they are to beincorporated, wherein the arm of the two outer rings is preferably of aplate member mounted on the outer end of the external outer ring, andwherein the arm of the other outer ring is likewise preferably formed bya plate, wherein the toothed rim itself is provided as a sintered metalinsert inserted into a recess in the plate material.
 13. An actuatoraccording to claim 7, characterized in that the arm of the other outerring consists of two relatively thin plates with flared edges and holerim and assembled with the plane sides toward each other, and whereinthe flared hole rim serves as a guide for the insert of sintered metal,and wherein arm and insert are mutually fixed preferably with a splinedconnection.
 14. An actuator according to claim 1, characterized in thatit is made or essentially made of sintered metal.
 15. An actuatoraccording to claim 1, characterized in that the motor (20) and thetransmission (21) are in-line with the planetary gear, i.e. the pullshaft of the motor and the power take-off of the transmission are inextension of the sun wheel of the planetary gear.
 16. An actuatoraccording to claim 1, characterized in that the transmission is formedby a number of planetary gears (80, 81, 82) coupled together.
 17. Anactuator according to claim 1, characterized in that the transmissioncomprises a worm drive with a worm (26) and at least one worm wheel(29), wherein the worm is driven by the motor shaft, and wherein theworm wheel drives a bevel wheel (30), which in turn drives a crown wheel(33) with a power take-off, preferably in the form of a sun wheel (35)in a subsequent planetary gear.
 18. An actuator according to claim 1,characterized in that it is incorporated fully or partly at the end of atube (10), preferably of polygonal cross-section, preferablyquadrangular cross-section.
 19. An actuator according to claim 18,characterized in that the tube is of extruded aluminium at least withscrew channels at the corners.
 20. An actuator according to claim 18,characterized in that the planetary gear is positioned against the endof the tube and secured to it.
 21. An actuator according to claim 20,characterized in that the outer rings are formed with screw holes forscrew attachment of the actuator in the screw channels of the aluminiumprofile.
 22. An actuator according to claim 18, characterized in thatthe planetary gear is positioned within the end of the tube, and thatthe mounting bracket of the intermediate ring is formed as; carrier inengagement with the profile.
 23. An actuator according to claim 19,characterized in that the end of the tube opposite the actuator isprovided with a mounting bracket corresponding to the mounting bracketon the outer ring of the planetary gear.
 24. An actuator according toclaim 18, characterized in that an actuator is provided at both ends ofthe tube, and that these are driven synchronously.
 25. An actuatoraccording to claim 1, characterized in that the intermediate ring isprovided with a cam (109) having a cam face which cooperates with atleast one switch (100) for controlling the electric motor.
 26. Anactuator according to claim 12, characterized in that it comprises anactivation pin (103), preferably parallel with the axis of the planetarygear, which is spring-loaded (104) such that an end of the pin is inengagement with the cam, whose cam face is perpendicular to the axis ofthe planetary gear, said pin being additionally connected to at leastone switch.
 27. An actuator according to claim 13, characterized in thatit comprises two end stop switches (101, 102) which are activated by thepin.
 28. An actuator according to claim 14, characterized in that itcomprises a leaf spring (107) which rests on the activation means of theend stop switches, and that the leaf spring is secured to the activationpin via a rocker arm, so that the leaf spring activates one switch whenthe pin is in one position and the other switch when the pin is in theother position.
 29. An actuator according to claim 1, characterized inthat it comprises a coil spring (120) which is fixed with one end andwound around a cylindrical element with a plurality of windings andarranged such that the spring allows free rotation or substantially freerotation in one direction of rotation of the element, but applies abraking force in the other direction of rotation of the element so thatthe actuator is self-blocking.
 30. An actuator according to claim 1,characterized in that it comprises an activatable coupling foruncoupling of the intermediate ring or the outer rings.
 31. An actuatoraccording to claim 28, characterized in that the coupling is formed by acoil spring (148).
 32. An actuator according to claim 28, characterizedin that the coupling force is adjustable for controlled return of theactuator.
 33. An actuator according to claim 18, characterized in thatthe power supply and the control electronics are incorporated in thetube, preferably in a cabinet (70) constructed for insertion into thetube end opposite the actuator.